[Olympus] Acceptance Simulations

[Belostotski, Stanislav]

Dear colleagues,
Dear Axel, as I understand you are not using track reconstruction in 
your simulations working only with generated tracks.
I see one more possible source of sistematics  in data analysis 
corresponding to one  toroid polarity running.
There might be a small offset in the reconstruction of the scattering 
angle with the help of (whatever) track reconstruction program. This 
offset may change the sign with changing the charge of the lepton (track 
curvature change the sign). Note that an offset of 1mrd  results 
typically in about 1% false asymmetry.
Luckily, to test that is purely MC job: you may see if there is any 
offset  by comparison of the generated and reconstructed theta's for e+ 
and e- tracks.
Best regards StanB

On 15.11.2012 12:59, Jan C. Bernauer wrote:
> Dear Norik,
>
>
>    as you know, we had to repair several ToFs after the last run. Their
> reduction in efficiency was certainly in that order of magnitude, if not
> larger, so I would say this test is very reasonable.
>
> If we see a large dependence of these tests on the magnetic field, we
> should consider running with two or three field settings. This may then
> allow us to tune the simulation later on.
>
> We should all think about measurements we can do to have enough
> redundant information to understand our detector and tune or simulation.
>
> Best,
> Jan
>
>
>
> On 15.11.12 12:28, Norair Akopov wrote:
>>
>> Dear Stan,
>>
>> I would not spend a time for quite unrealistic simulation, as you know
>> the old measurements with the cosmic as well the lates done with the SiPM
>> sandwiches with the beam have given ~99% efficiency. It means the
>> relaistic level of time dependence for the TOF efficiencies could be on
>> the level of max. 1-2% (even less), but not 20%? If you want to simulate
>> the extremely worse situation , then the forward and backward bars has to
>> differ on 1-2% efficiency.
>>
>> Regards,
>> Norik
>>       On Thu, 15 Nov 2012, Belostotski, Stanislav wrote:
>>
>>> Hi Axel, I suggest a simple test: assume that one  forward and one
>>> backward  TOF bar has lost its efficiency by some 20%. How the ratio at
>>> corresponding scattering angles would look like.
>>> Regards StanB
>>>
>>> On 14.11.2012 20:36, Axel Schmidt wrote:
>>>> Hi,
>>>>
>>>> I've analyzed another chunk of data, enough to double the statistics.  I'm attaching an updated version of my last plot.  There are definitely features that appear with the 1-degree binning.
>>>>
>>>> I agree, a generator that is uniform in lepton scattering angle is needed to study this further.  I'm working on producing that data now.  The advantage of the realistic generator is that I had that data lying around already; it was quicker to analyze.
>>>>
>>>> Cheers,
>>>> Axel
>>>>
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>>>>
>>>> On Nov 14, 2012, at 12:07 PM, Michael Kohl wrote:
>>>>
>>>>> Hi Axel,
>>>>> this looks good. On first sight, the acceptance changes are small.
>>>>> One needs much more statistics at backward angle. Maybe use a white generator with weights rather that cross-section distributed events.
>>>>>
>>>>> For the comparison of gap vs no gap, one would need to look at ratios of ratios.
>>>>>
>>>>> Thanks and best regards
>>>>>     Michael
>>>>>
>>>>>
>>>>>
>>>>> On Wed, 14 Nov 2012, Axel Schmidt wrote:
>>>>>
>>>>>> Hi Michael,
>>>>>> 	Here are plots showing the effect of introducing gaps between the tof bars (B+ mode only).  I show two different binning schemes side by side.
>>>>>> Cheers,
>>>>>> Axel
>>>>>>
>>>>>>
>>>>>
>>>>> +---------------------------------------------------------------------
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>>>>> | Email: kohlm at jlab.org
>>>>> | Cell:  +1-757-256-5122 (USA)
>>>>> |
>>>>> | Deutsches Elektronen-Synchrotron DESY, Bd. 66, Rm. 6,
>>>>> | Phone: +49-40-8998-6406, Cell: +49-171-101-1967
>>>>> +---------------------------------------------------------------------
>>>>
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